....look at pictures of early shihan and you will see most always have their index fingers extended.
As Chris already stated, the concept of asagao came from DR. Interesting point is that with asagao, the fingers still point the direction of your intent/ki, but since you have more than one finger extended, you can have your intent/ki focused in more than one direction at a time - just my opinion, of course, and YMMV.
I understand the idea here, but think about this. If ki flows from each finger and they are all pointing in different directions when spread, aren't you sending ki in to non-useful directions instead of using it to influence uke?
This reminds me of a quote from a project manager at my old engineering job. When part of the project was falling behind, the team was directed to "concentrate their resources" on that part to get it back on schedule. A couple of months passed and we met again with status reports. The part that was behind and in fact a little bit ahead of schedule, while other parts of the project had moved ahead a little slower than previously. The manager was very excited about the progress we had made on the task that had been behind schedule (completely ignoring the other parts of the project). His comment was that we should "concentrate our resources on EVERYTHING" and then we could all get ahead of schedule..... Hmmm, wait, that doesn't work. There's only so much effort to go around and if you spread it over all directions, less goes into your intended target.
This is exactly what I'm talking about on this issue. I still think the tea ceremony post put it best about aligning fingers along the arm to unify intent....
I'm looking forward to seeing more posts.....